1. Field of the Invention
The present invention relates to a process cartridge, an electrophotographic apparatus, an image forming method and an intermediate transfer belt.
2. Related Background Art
Image forming apparatus of electrophotographic system (electrophotographic apparatus) using an intermediate transfer belt is effective as a full color electrophotographic apparatus and a multi-color image forming apparatus that perform sequential laminated transfer of a plurality of component color images of full color image information or multi-color image information to output image forming product that is synthesized and reproduced from the full color image or the multi-color image.
Compared with a conventional transferring apparatus of a full color electrophotographic apparatus (for example, described in Japanese Patent Application Laid-Open No. 63-301960) having an electrophotographic apparatus wherein images are transferred from an electrophotographic photosensitive member to a second image bearing member fastened or attracted onto a transferring drum, a full color electrophotographic apparatus using an intermediate transfer belt does not require any processing or control on the transfer material but can transfer images from the intermediate transfer belt to a transfer material, and therefore has an advantage that various kinds of second image bearing member can be selected regardless of wideness/narrowness of width or longness/shortness of length to cover thin paper (40 g/m2 paper) to thick paper (200 g/m2 paper).
In addition, compared with such a case where rigid cylinder such as an intermediate transfer drum is used, adopting an intermediate belt shape, freedom for disposing inside an electrophotographic apparatus increases, giving rise to an advantage that miniaturization or cost reduction of the main body of the apparatus can be implemented by efficiently utilizing spaces.
However, the life of the intermediate transfer belt is shorter than the main body, and replacement is indispensable under the current state.
In addition, a waste toner container that collects residual developer (hereunder referred to as toner) in the intermediate transfer belt needs to be disposed and treated.
In addition to these, a lot of components such as electrophotographic photosensitive member, developing means and toner, etc. for a printer and a photocopier will need replacement.
As a method to unitize these replacement components and attach to/remove from the main body easily, Japanese Patent Application Laid-Open No. 8-137181 proposes to dispose an intermediate transfer belt and an electrophotographic photosensitive member as respectively independent units detachably mountable to the main body without difficulty.
However, these means involve a number of replacement units to make user""s operation complicated. Moreover, each unit is designed and disposed independently, thereby giving rise to such a problem that the main body gets larger or costs increase.
As means to solve this problem, replacing means to simultaneously remove from/attach to the main body the intermediate transfer belt and the electrophotographic photosensitive member (replacement components) as one-body unit are suitable, and are proposed in Japanese Patent Application Laid-Open No. 6-110261, Japanese Patent Application Laid-Open No. 10-177329 and Japanese Patent Application Laid-Open No. 11-30944 etc.
However, in the method to construct the intermediate transfer belt and the electrophotographic photosensitive member as one-body unit, that is, an intermediate transfer belt-electrophotographic photosensitive member integrated process cartridge (hereinafter to be referred to simply as xe2x80x9cintegrated process cartridgexe2x80x9d as well), the integrated process cartridge as a whole must be replaced even when a problem takes place in the intermediate transfer belt, which on the contrary might increase costs.
In general, in a full color electrophotographic apparatus, image density could be varied due to change in environments for use, or original correct color tone could become unavailable.
Therefore, in case of a full color electrophotographic apparatus using an intermediate transfer belt, it comprises density detecting means as means to obtain accurate density information, bringing density detecting toner image (patch) for respective colors produced on the intermediate transfer belt into radiation with a predetermined light so as to detect density from reflection rates of that reflection light and the intermediate transfer belt and to control image density by feeding the detection results back to the exposure amount and the developing bias, etc. Thus, it is important that glossiness of the surface of the intermediate transfer belt is stable all over the circumference of the belt.
However, at the time of shipment of the integrated process cartridge, or in the case where a user removes and conveys the integrated process cartridge, due to contact between the intermediate transfer belt and the electrophotographic photosensitive member, the intermediate transfer belt and the electrophotographic photosensitive member suffer from vibration, mutual friction, or rubbing frequently and repeatedly. Therefore, cuts and scrapes are given rise to onto the surface of the intermediate transfer belt, and glossiness of the intermediate transfer belt in the contact part decreases.
In addition, while the integrated process cartridge is kept for a long time at the time of shipment, components constructing the intermediate transfer belt and the electrophotographic photosensitive member are oozed so that the contact part fogs and the glossiness decreases.
In addition, increase in number of print causes accumulation of dirt on the surface of the intermediate transfer belt due to toner and paper dust, or occurrence of micro cuts or scratches so that the glossiness of the intermediate transfer belt decreases.
Moreover, in the intermediate transfer belt-electrophotographic photosensitive member integrated process cartridge, the intermediate transfer belt is always brought into contact with the electrophotographic photosensitive member, friction between the intermediate transfer belt and the electrophotographic photosensitive member not only reduces glossiness on the surface of the intermediate transfer belt as a whole but also gives rise to unevenness in glossiness. As a result, density detection is not executed accurately, giving rise to density unevenness for each image. In addition, a belt with glossiness unevenness from the initial period of use intensifies unevenness as it is used, and density unevenness on each image gets worse.
On the other hand, in the electrophotographic apparatus with the intermediate transfer belt and the electrophotographic photosensitive member being respectively independent units, even if the belt used has a glossiness unevenness, that unevenness changes little.
A purpose of the present invention is to provide an intermediate transfer belt-electrophotographic photosensitive member integrated process cartridge that makes maintenance easy, can attain miniaturization as well as cost reduction of the apparatus, can perform density detecting measuring for controlling image forming conditions in more stable and more accurate fashion, and can provide excellent images corresponding with use conditions, a electrophotographic apparatus having the above-described process cartridge, and an image forming method using the above-described electrophotographic apparatus.
In order to solve the above-described problem, the present inventors have intensified their consideration and found out that it works well with the average glossiness of the intermediate transfer belt being 30 to 90 and its deviation being within 10.
Moreover, the intermediate transfer belt-electrophotographic photosensitive member integrated process cartridge mostly is at a standstill with tension being applied for a long period until it is actually used, bending habit will be given in the portion of a spanning roller, execution of density detection in this portion does not provide accurate reflection light, giving rise to density unevenness in each image as a result thereof.
Also, in order to solve the above-described problem, the present inventors have intensified their consideration and found out that it works well with the average film thickness of the intermediate transfer belt being 40 xcexcm to 200 xcexcm and further with its unevenness being within xc2x120% relative to the average value.
That is, the present invention provides a process cartridge detachably mountable to an electrophotographic apparatus main body, the process cartridge integrally comprising:
an electrophotographic photosensitive member to carry a toner image;
an intermediate transfer belt having a contact part with the electrophotographic photosensitive member;
primary transfer means to primarily transfer the toner image at the contact part from the electrophotographic photosensitive member to the intermediate transfer belt; and
electric charge providing means to give electric charges in polarity opposite to the polarity of the toner at the time of the primary transfer to the toner on the intermediate transfer belt to return the toner on the intermediate transfer belt to the electrophotographic photosensitive member at the contact part to clean the intermediate transfer belt,
wherein the intermediate transfer belt has an average glossiness, obtained in the circumference direction, of 30 to 90;
a glossiness deviation of within 10;
an average film thickness of 40 to 200 xcexcm; and
a film thickness unevenness of within xc2x120% relative to the average film thickness.
In addition, the present invention provides an electrophotographic apparatus comprising:
an electrophotographic photosensitive member to carry a toner image;
charging means to charge the electrophotographic photosensitive member;
exposing means to form an electrostatic latent image on the electrophotographic photosensitive member charged with the charging means;
developing means to develop with toner the electrostatic latent image on the electrophotographic photosensitive member formed with the exposing means to form a toner image on the electrophotographic photosensitive member;
an intermediate transfer belt having a contact part with the electrophotographic photosensitive member to perform, after the primary transfer of the toner image from the electrophotographic photosensitive member to the intermediate transfer belt, secondary transfer of the primarily transferred toner image to a transfer material;
primary transfer means to primarily transfer the toner image from the electrophotographic photosensitive member to the intermediate transfer belt at the contact part;
electric charge providing means to give electric charges in polarity opposite to the polarity of the toner at the time of the primary transfer to the toner on the intermediate transfer belt to return the toner on the intermediate transfer belt to the electrophotographic photosensitive member at the contact part to clean the intermediate transfer belt, and
a process cartridge integrally comprising at least the electrophotographic photosensitive member, the intermediate transfer belt, the primary transfer means and the electric charge providing means and being detachably mountable to the electrophotographic apparatus main body,
wherein the intermediate transfer belt has an average glossiness, obtained in the circumference direction, of 30 to 90;
a glossiness deviation of within 10;
an average film thickness of 40 to 200 xcexcm; and
a film thickness unevenness of within xc2x120% relative to the average film thickness.
In addition, the present invention provides an image forming method comprising:
a charging step to charge an electrophotographic photosensitive member;
an exposing step to form an electrostatic latent image on the electrophotographic photosensitive member charged in the charging step;
a developing step to develop with a toner the electrostatic latent image on the electrophotographic photosensitive member formed in the exposing step to form a toner image on the electrophotographic photosensitive member;
a primary transfer step to primarily transfer the toner image formed in the developing step, with primary transfer means, from the electrophotographic photosensitive member to the intermediate transfer belt having a contact part with the electrophotographic photosensitive member;
a secondary transfer step to secondarily transfer the toner image primarily transferred in the primary transfer step to a transfer material;
an electric charge providing step to give electric charges in polarity opposite to the polarity of the toner at the time of the primary transfer step to the toner on the intermediate transfer belt with electric charge providing means; and
an intermediate transfer belt cleaning step to return the toner on the intermediate transfer belt to the electrophotographic photosensitive member at the contact part to clean the intermediate transfer belt,
the image forming method using the electrophotographic apparatus having a process cartridge, the process cartridge integrally comprising at least the electrophotographic photosensitive member, the intermediate transfer belt, the primary transfer means and the electric charge providing means and being detachably mountable to the electrophotographic apparatus main body,
wherein the intermediate transfer belt has an average glossiness, obtained in the circumference direction, of 30 to 90;
a glossiness deviation of within 10;
an average film thickness of 40 to 200 xcexcm; and
a film thickness unevenness of within xc2x120% relative to the average film thickness.
In addition, the present invention is an intermediate transfer belt for the above-described process cartridge.
Incidentally, in Japanese Patent Application Laid-Open No. 10-63111, a method to decrease changes in glossiness of the intermediate transfer member is disclosed and only the average glossiness of the intermediate transfer belt is described. There are no statements on film thickness of the intermediate transfer belt and its unevenness.
In addition, in Japanese Patent Application Laid-Open No. 5-31818, a method of producing a belt having uniform surface is disclosed. There are no statements on film thickness of the intermediate transfer belt and its unevenness.